The present invention relates to disposable diapers.
Conventionally, the typical disposable diapers employ moisture-permeable but liquid-impermeable film, for example, resinous film mixed with inorganic fine particles as a backsheet in order to eliminate or alleviate unpleasant stuffiness often experienced by diaper wearers.
Such backsheet has a moisture permeability in the order of 1500 to 3000 g/m.sup.2 24hs (ASTM E96-66) and a water pressure resistance of 1000 cmH.sub.2 O or higher (JIS L 1092). These values have been found to be sufficient for urine-impermeability but insufficient for a desired moisture-permeability. Therefore, the stuffiness generated within the diaper can not be suppressed or alleviated by such a backsheet to the desired level where the wearers are not given any discomfort and are substantially free from any adverse effect of stuffiness that would possibly cause a skin disease. The higher the moisture-permeability of the backsheet, the lower the liquid-impermeability thereof should be, resulting in leakage of liquid excretion. Confronting such an antinomic relationship, the highest priority is usually given to -the liquid-impermeability.
The typical example of the open type disposable diaper having tape fastener means used to fasten front and rear bodies to each other at the level of waist line is disclosed in Japanese Patent No. 1977-40267. This example comprises a liquid-permeable topsheet, a liquid-impermeable backsheet, and a liquid-absorbent panel sandwiched therebetween wherein a pair of side flaps are formed by portions of the top- and backsheets extending outward beyond laterally opposite sides of the panel and the respective side flaps are formed at the crotch level with cutouts destined to define leg-openings around which the respective side flaps are provided with elastic members serving to seal the side flaps around the respective legs of the wearer and wherein the rear body is provided at laterally opposite sides with tape fasteners used to fasten the rear body to the front body.
As the diaper disclosed by the above-identified Japanese Patent No. 1977-40267 is typical, the cutouts formed in opposite sides of the crotch zone for improved fitness of the diaper to the wearer's body necessarily reduce the width of the crotch zone and it is practically impossible for the crotch zone to surround the wearer's thighs. The crotch zone thus width-reduced inevitably decreases the ability of the crotch zone to absorb liquid excretion and to catch solid excretion, so leakage of excretion, particularly liquid excretion, readily occurs along opposite side edges of the crotch zone.
Generally in the well known diaper of the type as disclosed by the above-identified Japanese Patent, a fold line of the crotch zone corresponding to the boundary line of the front and rear bodies extends horizontally and in parallel to the waist line. In addition, the liquid-absorbent panel has so-called semi-rigidity, since it often comprises a more or less compressed accumulation of fluff pulp and tissue paper covering top- and back surfaces of this accumulation. Accordingly, the crotch zone of the diaper is not able to fit the corresponding zone of the wearer's body, thus not only giving the wearer the feeling of incompatibility but also causing said leakage.